/Engine/Plugins/MovieScene/MovieRenderPipeline/Source/MovieRenderPipelineCore/Public/MovieRenderTileImage.h
Accumulate a single tile to this plane. The raw data must be the exact size of the tile. In general, SampleOffsetX/SampleOffsetY will be 0 or 1. In most cases it is zero, but but if a sample has a subpixel offset after the last sample, it will affect the first sample of the next pixel. All accumulating assumes edge clamping.
void AccumulateSinglePlane ( const TArray64< float > & InRawData, int32 InSizeX, int32 InSizeY, float InSampleWeight, int InSampleOffsetX, int InSampleOffsetY )